Field of the Invention
This invention relates to apparatus for recording multilevel segmented data signals such as analog time codes involving zero and one levels and time tick marks on a record medium.
Description of the Prior Art
Apparatus for printing letters, numerals and other symbols upon moving record surfaces are known in the prior art. An example of such apparatus is shown in U.S. Pat. No. 3,157,879 which shows a cathode ray tube for printing information by means of an electron beam upon an externally located heat sensitive surface. In this apparatus, an electron-permeable window is provided in the face of the cathode ray tube and an element of dielectric material having a plurality of channels adapted to pass electrons is arranged over the window. Electrical potentials are individually applied to the channels to control the selective passage by the channels of electrons. As the electron beam is swept over the window, the electrical potentials determines which of the channels can pass the electron beam to impinge upon the heat sensitive recording medium.
Another form of such apparatus is shown in U.S. Pat. No. 3,210,597 wherein the faceplate of a cathode ray tube is provided with a fiber-optics bundle for transmitting to a recording medium light produced internally of the cathode ray tube by the electron beam. The fiber-optics bundle is comprised of smooth fibers of transparent materials, such as glass. Such fibers transmit light with high efficiency by means of multiple internal reflections. Each fiber in an array or bundle transmits its light independently of adjacent fibers.
Still other forms of known prior art apparatus for printing or placing symbols upon a recording medium include closely spaced light emitting diodes and small arcing flash heads.
A disadvantage common to the cathode ray tube and light emitting diode forms of the prior art apparatus is the high cost of the apparatus. Thus, while the cathode ray tube arrangements provide proven technology, they are quite expensive. Light emitting diodes require a special array which in small quantities would be prohibitively expensive.
A further disadvantage of light emitting diodes is their low light output. Their use, therefore, would tend to result in marginal operation of the recording apparatus, particularly at higher recording or chart speeds, for example, several hundred centimeters per second. Moreover, point source light emitting diodes of the proper wavelength light output, for example, 360 nanometers, to match the sensitivity of the recording medium, are required. Such light emitting diodes are not commonly available. Fiber-optics cathode ray tubes and small arcing flash heads have these same disadvantages also. Additionally, while relatively inexpensive, small arcing flash heads emit large quantities of undesired electromagnetic radiations which result in undesired and in many cases intolerable radio frequency interference (RFI).
A less expensive and more desirable form of apparatus for printing and placing symbols on a recording medium, is disclosed in my copending application bearing Ser. No. 616,609, filed Sept. 25, 1975, and assigned to the assignee of the present invention. That form of apparatus includes three Xenon tubes and a separate tapered fiber optics bundle associated with each of the flash tubes. The fiber optics bundles concentrate the flash tube images to form relatively small line segments which are disposed in an H-shaped recording array. When placed in cooperative relation with a light sensitive recording medium that is ultrasensitive to a predominant wavelength of the light produced by said flash tubes, selective and appropriate flashing of said flash tubes produces dense analog time code and other traces on said recording medium.
The requirement in such apparatus, however, for a tapered fiber optics bundle for each of the flash tubes also leaves something to be desired from the standpoints of cost, light availability, reliability and maintainability.